Compact scroll fan assembly

ABSTRACT

A radial fan assembly for use in a powered air purifying respirator includes at least an impeller, a printed circuit board and a scroll casing. The scroll casing has a first and a second scroll casing element. The second scroll casing element includes at least a portion of the printed circuit board. When the radial fan assembly is used in a powered air purifying respirators, the respirator may also include components such as a filter assembly.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 61/379,113, filed Sep. 1, 2010, the disclosure of whichis referenced in its entirety herein.

FIELD OF DISCLOSURE

The present disclosure pertains to a radial fan assembly for use in apowered air purifying respirator, where the scroll casing includes atleast a portion of a printed circuit board.

BACKGROUND

Scroll fans, also known as radial or centrifugal fans, are used in avariety of devices and for a variety of purposes. Applications include,for example, climate control, vehicle and machinery cooling systems,personal comfort, ventilation, fume extraction, removing dust, anddrying. Specifically, scroll fans may be used in any number of devicesranging from hair dryers and leaf blowers to cooling units for personalcomputers and powered air purifying respirators.

A typical scroll fan has a scroll-shaped casing and a moving component,called an impeller. The impeller often consists of a central shaft aboutwhich a set of blades or ribs are positioned. Air typically enters thefan in or near the shaft. It then moves from the shaft to the opening inthe scroll-shaped fan casing as the impeller is rotated. The air is spunoutwards to the outlet by deflection and centrifugal force. Scroll fansblow air out at an angle that is oblique or perpendicular to the intakeof the fan. Scroll fans can produce more pressure for a given air volumethan other types of fans, which can be desirable for particularapplications, such as those mentioned above.

In addition to a scroll-shaped casing and an impeller, scroll fans alsotypically include a motor, and often control circuitry. A traditionalscroll fan construction has a scroll casing, an impeller enclosed withinthe scroll casing, a motor to rotate the impeller, and often a smallprinted circuit board (PCB) mounted within the motor. The motor and PCBcan then be connected via a connector ribbon or other means to a largerprinted circuit board. The scroll and larger PCB are then housed withintheir specific device.

Space can be an important constraining factor for any scroll fan design.Powered air purifying respirators (PAPR) are no exception. PAPR'scontaining scroll fans can come in a variety of designs including hoods,helmets, face masks, suits, belt mounted respirators and other forms. Inmany of these designs, particularly where the PAPR is intended to beportable or transported by the wearer, creating an lightweight,ergonomic, and compact design is particularly important.

SUMMARY

In one aspect, the present disclosure is directed to a radial fanassembly for use in a powered air purifying respirator. The radial fanassembly includes at least an impeller, a printed circuit board, and ascroll casing. The scroll casing includes a first scroll casing elementand a second scroll casing element. The second scroll casing elementincludes at least a portion of the printed circuit board.

In another aspect, the present disclosure is directed to a powered airpurifying respirator (PAPR). The PAPR includes at least a filterassembly and a radial fan assembly. The radial fan assembly includes ascroll casing. The scroll casing includes at least a portion of aprinted circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 shows an exemplary powered air purifying respirator.

FIG. 2 shows an exploded view of a blower assembly with a compact scrollfan assembly for use in a powered air purifying respirator.

FIG. 3 shows a top view of a compact scroll fan assembly.

FIG. 4 shows an exploded view of a compact scroll fan assembly.

FIG. 5 shows a cut-away view of a blower assembly.

FIG. 6 shows a top view of an exemplary printed circuit board consistentwith the present disclosure.

In the following description of the illustrated embodiments, referenceis made to the accompanying drawings, in which are shown by way ofillustration, various embodiments in which the invention may bepracticed. It is to be understood that the embodiments may be utilized,and structural changes may be made, without departing from the scope ofthe present invention. The figures are not necessarily to scale. Likenumbers used in the figures refer to like components. However, it willbe understood that the use of a number to refer to a component in agiven figure is not intended to limit the component in another figurelabeled with the same number.

DETAILED DESCRIPTION

The present invention now will be described more fully with reference tothe accompanying drawings, in which preferred embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

FIG. 1 shows an exemplary powered air purifying respirator 10 (PAPR). Apowered air purifying respirator is a commonly used type of respiratorfor working in areas where there is known to be, or there is a risk ofthere being, dusts, fumes or gases that are potentially harmful orhazardous to health. A PAPR has a blower assembly 18 including a fandriven by an electric motor for delivering a forced flower of air to therespirator user. A filter(s) is fitted to the blower assembly throughwhich air is drawn by the fan. The air is passed from the blowerassembly 18 through a breathing tube or hose 16 to a contained user 11environment. Such an environment is often surrounded by a face shield 14(as illustrated in FIG. 1), head piece, or suit. In the illustratedembodiment, the face shield also includes a protective helmet 12. Thehose 16 thus provides filtered air to the user's breathing zone 58.

Face shield 14 can be relatively transparent to allow a wearer goodvisibility and may be made of polycarbonate materials or any othersuitable material. Protective helmet 12 can further include a sealingmember or face seal 13 that makes contact with a user's face to providea barrier between the filtered air within the breathing zone 58 of theuser and the outside environment. Face shield 14 may be molded as asingle unit or may include multiple components later attached to eachother, or may be constructed by any other appropriate method.

In the illustrated configuration, blower assembly 18 is mounted to abelt 19 and is worn by a user 11 around the waist. Alternatively, ablower assembly can be mounted to a backpack or any other device thatallows a user to wear or carry blower assembly 18. A hose 16 is used todirect air flow from the blower assembly 18 to the user's breathing zone58 as contained by face shield 14 and helmet 12 in the illustratedembodiment.

While one particular construction for a PAPR is described above, anyvariety or configuration of PAPR can be used in accordance with thepresent disclosure. For example, in one configuration, the filter andblower assembly may be mounted directly into a protective helmet or intoa facepiece (also known as a breath assisted PAPR).

FIG. 2 shows an exploded view of a blower assembly 20 with a compactradial or scroll fan assembly 30 for use in a powered air purifyingrespirator. Because many PAPR's are worn or transported by a user asdescribed above, size, weight, and shape of the blower assembly areimportant factors, and can contribute to the comfort and mobility of theuser. The fan is an important component within a PAPR. In addition tomotor efficiency and speed, factors like impeller diameter, blade designand scroll casing seal can impact the air pressure and volume providedto the user.

FIG. 2 shows an example of a compact radial fan assembly 30 that iscapable of reducing overall space required for fan assembly 30 withinblower assembly 20 while maintaining air volume and pressure levels.Blower back casing 22 provides an outer structure for blower assembly20. Back casing 22 can include clips, slots that a strap can be lacedthrough, interlocking devices, or one or more other features forattaching blower assembly 20 to a belt, harness, back pack or other itemthat can be worn or transported by a user. In the illustratedembodiment, fan assembly 30 fits adjacent to blower back casing 22. Fanassembly 30 includes a first scroll casing element 34 and a printedcircuit board (PCB) 31, which serves as a second scroll casing elementin this embodiment. First scroll casing element 34 can be any portion ofa scroll casing that serves to direct or contain airflow through ascroll fan. First scroll casing element 34 can have any workable shape,including but not limited to, a cylindrical shape or a bowl-like shape.First scroll casing element 34 can be molded, cast, pressed or formed byany other appropriate manufacturing method.

Second scroll casing element also can be any portion of a scroll casingthat serves to direct or contain airflow through a scroll fan. While PCB31 serves as second scroll casing element in the illustrated embodiment,PCB 31 may be only a part of second scroll casing element. For example,additional components made of any appropriate material may be secured toPCB 31 to form second scroll casing element when combined.

First scroll casing element 34 is mounted to PCB 31 to form a path forair drawn through filter component 26, rotated about the scroll, andprovided to the user. Printed circuit board 31 may use organic orinorganic base materials in a single or multilayer, rigid or flexibleform. Blower front casing 24, the portion of the blower casing facingaway from a wearer's body, fits over fan assembly 30 and connects toblower back casing 22. A filter component 26 fits into the front ofblower front casing 24. Filter component 26 can be attached to blowerfront casing 24 by a variety of methods, for example, by using clips,screws, snaps, sliding filter component 26 into a slot, or by any othermethod known in the art. This construction allows fan assembly to drawambient air through filter component 26, into an impeller 36 and aroundthe scroll casing (as illustrated in later figures), and force air to auser's breathing zone via outlet 37.

Filter component 26 can include any one or more of a variety ofmaterials and can target a variety of substances. For example, filtercomponent 26 can include a traditional filter bed, a pleated medium, orany other type of filtering medium or combination of media. The filtermedium can include a particulate filtering medium, a chemical filteringmedium, or any combination of the two. A chemical filtering medium mayinclude one or more of a sorbent, a catalyst or a chemically reactivemedium and may target gases such as ammonia, methylamine, formaldehyde,chlorine, hydrogen chloride, sulfur dioxide, acidic gases, organicvapors or any other desired gas or contaminant. In one embodiment,filter component 26 can be curved to provide a more compact or ergonomicconstruction.

Blower assembly 20 can be configured in a variety of different ways. Fanassembly 30 is preferably disposed downstream of filter component 26 toprevent fan assembly 30 from collecting contaminants from the ambientair. However, in an alternative embodiment, filter component 26 could belocated downstream of fan assembly 30. In another alternativeembodiment, blower casing could be designed as a single component,instead of including blower back casing 22 and blower front casing 24.Blower casing could also have more than two components, or include onlytwo components arranged in a different configuration than thatillustrated. Blower assembly 20 also can be configured to fit inside orbe mounted to a helmet or facepiece, or to be used with any other typeof PAPR.

FIG. 3 shows a top view of a compact fan scroll assembly 30. Firstscroll casing element 34 is mounted to printed circuit board 31 usingscrews 51 to form scroll fan casing 54. Alternatively, any othermounting method or device, such as clips, clamps, snaps, pins or anyother method known in the art can be used to secure first scroll casingelement 34 to printed circuit board 31. Gasket 61 or another sealingelement can be disposed between PCB 31 and the edge of first scrollcasing element 34 to provide an air-tight or near air-tight seal betweenPCB 31 and first scroll casing element 34. Gasket 61 can be made of anyappropriate material including an elastomeric material such as a type offoam or rubber. In the illustrated embodiment, PCB 31 also has othercomponents mounted to it, including battery connector 35 and otherdiscrete electrical components 42 such as transistors, amicrocontroller, diodes, resisters, and other components used in thecontrol circuitry for blower assembly 20 and even other parts of a PAPR.

FIG. 4 shows an exploded view of a compact scroll fan assembly 30. PCB31 serves as a scroll casing component such that it is a portion of thescroll casing and directs or contains airflow within a fan scroll. PCB31 also serves as a mounting surface for motor 55. Motor 55 includes atleast stator 32, rotor assembly 33, bearing tower 62, and hall effectsensors 68. Stator 32 can be soldered or otherwise secured to PCB 31.Bearing tower 62 can be attached or secured to the side of PCB 31opposite the side stator 32 was secured to. Bearing tower 62 can beattached to PCB 31 using screws or any other fastening method known inthe art. Rotor 33 can be mounted over stator 32. Hall effect sensors 68can be secured on PCB 31 by a method such as soldering and serve tosense the position of the rotor 33. This information can be fed back toa motor controller (not shown) to allow for more precise motor control.

One advantage of mounting both motor 55 and first scroll fan casingelement 34 to PCB 31 is the availability of a single, larger sized PCB31 for meeting design and safety requirements for intrinsically safeapplications. Traditional motor designs have a smaller PCB mountedinside motor 55, and a connector is used to connect motor 55 to itscorresponding drive and safety components, which are typically mountedon a second PCB. Mounting motor 55 to a larger PCB 31 allows driveelectronics and safety components for the motor to be directly mountedto the same PCB 31. Examples of safety components include diodes used toprevent motor voltage from exceeding maximum levels. These componentscan then be connected to motor 55 using traces in the PCB instead ofrequiring additional connector components or ribbons. This is turn canreduce the likelihood of connection failure or sparking, and enable thedesign to meet safety requirements for certification for use inhazardous locations.

Impeller 36 is mounted to rotor assembly 33. In one embodiment, impeller36 can be mounted to rotor assembly 33 using friction. Alternatively,impeller 36 can be molded directly over rotor assembly 33, secured torotor assembly 33 using adhesive, or secured by any other appropriatemethod. First scroll casing element 34 is finally mounted to PCB 31, andtogether with PCB 31, forms scroll casing 54 for scroll fan assembly 30.As illustrated, only a portion of PCB 31 forms part of scroll casing 54in this embodiment. In alternate embodiments, a larger or smallersurface area of PCB 31 could be used as part of scroll casing 54.Alternatively, more than two components could be used to form scrollcasing 54.

Stator 32, rotor assembly 33, bearing tower 62 and hall effect sensors68 combine to form an electric motor 55 which rotates impeller 36. Asimpeller 36 rotates, it draws ambient air through inlet 38. Blades 52 ofimpeller 36 force air around the curve of air passageway 53 of scrollcasing 54 formed by both first scroll casing element 34 and PCB 31.Outlet piece 37 attaches to scroll casing 54. Outlet piece 37 canconnect hose 16 (shown in FIG. 1) to scroll casing 34 to ensure airflowbetween scroll fan assembly 30 and a user's breathing zone 58 (shown inFIG. 1).

Electric motor 55 can be any type of motor appropriate for use with ascroll fan. For example, it may be a direct current (DC) motor, such asa brushless or brushed DC motor. An alternating current (AC) motor canalso be used, such as an AC induction or AC synchronous motor. Whenbatteries are used to power a PAPR, use of a DC motor may be moreadvantageous than an AC motor because use of an AC motor requires theadditional use of a power inverter to convert DC power into a usableform for the AC motor.

When batteries are used to provide power to a blower assembly 20 in aPAPR 10, a variety of batteries, including lithium ion, nickel metalhydride, or nickel cadmium can be used. Batteries can be connected toPAPR 10 in any desired way. For example, batteries could be housedwithin blower assembly 20, exteriorly attached to blower assembly 20,attached via a cable to blower center 20, or by any other means. In oneembodiment, battery connector assembly 35 can be designed to provide anair-tight seal to batteries to prevent contamination of connector pinsby dust or other potentially harmful contaminants.

In the illustrated embodiments, impeller 36 has backward inclined blades52, but impeller 36 may have any appropriate blade design, for example,forward curved blades, flat blades, or any other workable design.Impeller 36 can be manufactured in several different pieces that arelater secured to each other, or the entire impeller 36 can be a unitaryconstruction. For example, a base and blades of the impeller 36 may bemolded as a single component and later secured to an annularconstruction, such as a ring, to form impeller 36. Impeller 36 can bemolded or made by any other appropriate method.

FIG. 5 shows a cut-away view of blower assembly 20. In this illustratedembodiment, blower back casing 22 forms the portion of blower casingnearest the wearer. T-shaped clips 44 protrude from blower back casing22 and can be used to secure the blower assembly 20 to a belt or othertype of strap, carrier or garment. In this instance, the surface ofblower back casing 22 is slightly curved to conform to a wearer's waist.PCB 31 may be located adjacent to blower back casing 22. While PCB 31 isrigid in this particular embodiment, PCB 31 could alternatively beflexible to conform more to the shape of blower back casing 22 or anyother piece of blower casing. A flexible PCB includes a printed circuitproduced on a flexible substrate, allowing it to be folded or bent. Aflexible PCB may enable circuitry to better fit into the available spaceor to allow better movement.

Motor 55, including bearing tower 62, stator 32 and rotor 33, is mountedto PCB 31. Impeller 36 is rotated by motor 55. First scroll casingelement 34 is secured to PCB 31, and in this instance, covers theimpeller 36 and motor 55, while providing an opening for inlet 38.Blower front casing 24 covers the impeller and, in this instance,connects to blower back casing 22 to encase scroll fan assembly 30. Asmentioned above, any type of blower casing known in the art can be usedconsistent with the present disclosure. Filter component 26 is mountedto the top (as illustrated) or outer-facing surface of front blowercasing 22. As mentioned above, filter component 26 can be secured toblower casing or within blower casing using any attachment method, suchas clips, screws, snaps, sliding filter component 26 into a slot, or byany other method known in the art. Filter component 26 can bealternatively disposed downstream of scroll fan assembly 30, or in anyother desired location on the PAPR.

FIG. 6 shows a top view of a printed circuit board 31 consistent withthe present disclosure. In the present instance, stator 32, batteryconnector assembly 35 and other electrical components 42 are mounted toPCB 31. Additionally, a sensor 43 can be mounted to PCB 31. In oneembodiment, sensor 43 is in an air flow path of the scroll fan assembly30.

Any type of PCB 31 known in the art can be used, consistent with thepresent disclosure. A PCB is generally used to mechanically support andelectrically connect electronic components using conductive pathways ortraces 57. PCB's and their traces can be made in a variety of ways. Forexample, the traces 57 can be etched from copper sheets laminated onto anon-conductive substrate. A substrate can be made out of a variety ofmaterials. For example, it may be made of multiple layers of dielectriclaminated together with epoxy resin pre-impregnated fibers. One commonlyused dielectric is polytetrafluoroethylene. Pre-impregnated fibers maybe, for example, phenolic cotton paper, cotton paper and epoxy, wovenglass and epoxy, matte glass and polyester, etc. After the layers ofepoxy are laminated together, they can be coated with a conducting layermade of, for example, a thin copper foil.

Traces 57 can be created by several different methods. For example,using a silk screen method, unwanted copper can be removed afterapplying a temporary mask, thus leaving only the desired copper traces.Such a mask over desired copper traces can be created by using silkscreen printing to apply etch resistant inks to protect the copper foil.Subsequent etching can then remove the unwanted ink. A photoengravingmethod uses a photomask and chemical etching to remove the copper foilfrom the substrate. A photomask can be prepared with a photoplotterusing data provided by a technician using computer-aided manufacturingsoftware. PCB milling uses a two or three-axis mechanical milling systemto mill away copper foil from the substrate. Milling can be especiallyuseful for smaller quantities or prototype quantities. Traces 57 canalso be created by additive processes where a reverse mask is appliedover the copper or conductive layer on the PCB so that only the desiredtraces show through. Additional copper or conductive material can thenbe plated onto the board in the unmasked areas.

PCB 31 can have traces on both of its major surfaces. Vias, holesdrilled through a PCB, are often filled with annular rings of conductivematerial to allow thermal and electrical connection of conductors ortraces on opposite sides of a PCB. Additionally, some PCB's, known asmulti-layer PCB's have trace layers inside the PCB. These can be formedby bonding together separately etched thin boards.

Traces 57 on PCB 31 can be coated with materials such as photo resist toprevent the etching away of exposed copper. Areas that should not besoldered or contain no traces can be covered with a solder mask coating.Such a coating can prevent solder from bridging between conductors andcreating short circuits.

Other coatings can be applied to PCB 31. For example, a conformalcoating such as an epoxy resin or silicone can be applied to the entiresurface of a PCB or just a portion of a surface of the PCB. For example,the portion of PCB 31 nearest the first scroll casing element can besealed with a conformal coating. One exemplary coating is 3M™ Novec™coating fluid, manufactured by 3M Company of St. Paul, Minn. Coatingscan serve to seal any exposed traces or vias on a surface of the PCB andprovide protection to the surface of a PCB in addition to protecting anycomponents mounted to the surface of the PCB. In some embodiments, sucha coating on a side of the PCB nearest the first scroll element canserve as a fluidic barrier. This can increase efficiency of the fan, andin turn, the PAPR.

Sensor 43 can be mounted to any appropriate location on PCB 31, on thesame surface of PCB 31 that first scroll casing element 34 is mountedtoo. Additionally, sensor 43 may be mounted to the opposite side of PCB31 or may be mounted to an area in the air path of the scroll fan, suchthat it is disposed in an interior of the scroll casing. Sensor 43 canmonitor parameters such as temperature, air pressure, motor position,motor speed, or any other desired parameter. Examples of sensors thatcould be used consistent with the present disclosure include the MPL115ADigital Barometer distributed by Freescale™ of Austin, Tex., or an ASDXSeries Pressure Sensor distributed by Honeywell, Inc. of Morristown,N.J., or any other appropriate sensor.

Other electrical components 42, passive or active, can be mounted at anydesired location on PCB 31. For example, a microprocessor, resistor,capacitor, transistor, diode, relay, wireless transceiver or any otheror combination of such components may be used consistent with thepresent disclosure. Components 42 can be mounted in an interior of thescroll casing, on an exterior of the scroll casing, or on a side of PCB31 opposite first scroll casing element.

Electronics 42 can be control electronics for any portion of the PAPR,or for the entire PAPR. Control electronics 42 can be used for example,to govern the rate of airflow of the PAPR, calculate remaining batterylife, monitor filter loading and any other desired parameter.

Connector 35, such as a separate component or one or more conductors,can be used to connect PCB 31 and any components on it to a powersource. As discussed above, in one embodiment, a power source can be abattery. Alternatively, it may be a form of AC power. A power source forPCB 31 can be disposed in any desired manner. For example, it may bemounted to PCB 31, electrically to PCB 31 and mounted elsewhere, orunmounted.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this invention pertains havingthe benefit of the teachings presented in the foregoing descriptions andthe associated drawings. Therefore, it is to be understood that theinvention is not to be limited to the specific embodiments disclosed andthat modifications and other embodiments are intended to be includedwithin the scope of the appended claims. Although specific terms areemployed herein, they are used in a generic and descriptive sense onlyand not for purposes of limitation.

What is claimed is:
 1. A motor driven air purifying respirator comprising: a blower assembly including: a back casing fixed to a front casing; a filter assembly comprising a filter component chosen from the group consisting of a particulate filtering medium, a chemical filtering medium, and combinations thereof, for purifying the air drawn therethrough; the motor including a rotor and a stator; a radial fan assembly including at least an impeller that is driven by the motor and a volute with an air inlet which is configured to receive the purified air from the filter component, and to direct the purified air outward through an air outlet of the volute; and wherein the volute comprises a spiral shaped casing element and a printed circuit board, wherein the spiral shaped casing element is mounted to a first surface of the printed circuit board such that a flowpath for the purified air forced by the impeller through the volute is defined by the first surface of the printed circuit board and an interior surface of the spiral shaped casing element; and wherein the motor of the radial fan assembly is located within the volute and the stator is mounted on the first surface of the printed circuit board; wherein the radial fan assembly is axially located in a space enclosed between the front casing and the back casing and the filter assembly is mounted on a front face of the front casing, such that the filter assembly resides outside the space enclosed between the back casing and the front casing in which the radial fan assembly resides.
 2. The motor driven air purifying respirator of claim 1, further comprising a sealing element that is disposed between the printed circuit board and an edge of the spiral shaped casing element to provide an air-tight seal between the printed circuit board and the spiral shaped casing element.
 3. The motor driven air purifying respirator of claim 1, wherein the printed circuit board is a fluidic barrier.
 4. The motor driven air purifying respirator of claim 3, wherein a side of the printed circuit board nearest the spiral shaped casing element is sealed with a conformal coating.
 5. The motor driven air purifying respirator of claim 1, wherein the printed circuit board is flexible.
 6. The motor driven air purifying respirator of claim 1, further comprising a discrete electrical component, wherein the discrete electrical component is mounted to the first surface of the printed circuit board.
 7. The motor driven air purifying respirator of claim 1, further comprising a pressure sensor, wherein the pressure sensor is mounted to a second surface that is opposite from the first surface of the printed circuit board that the spiral shaped casing element is mounted to.
 8. The motor driven air purifying respirator of claim 1, further comprising control electronics for the motor driven air purifying respirator, wherein at least a portion of the control electronics are mounted on the printed circuit board.
 9. The motor driven air purifying respirator of claim 8, wherein the control electronics comprise a microprocessor, and wherein the microprocessor is mounted to the printed circuit board.
 10. The motor driven air purifying respirator of claim 1 wherein the printed circuit board that defines the volute is the only printed circuit board comprised by the radial fan assembly.
 11. The motor driven air purifying respirator of claim 1, wherein the spiral shaped casing element defines the entirety of the air inlet and the entirety of the air outlet, and wherein the printed circuit board does not define any portion of the air inlet or of the air outlet.
 12. A motor driven air purifying respirator comprising: a blower assembly including: a back casing fixed to a front casing; a filter assembly comprising a filter component that is a chemical filtering medium chosen from the group consisting of a sorbent, a catalyst, a chemically reactive medium, and combinations thereof, for purifying the air drawn therethrough; the motor including a rotor and a stator; a radial fan assembly including at least an impeller that is driven by the motor and a volute with an air inlet which is configured to receive the purified air from the filter component, and to direct the purified air outward through an air outlet of the volute; and wherein the volute comprises a spiral shaped casing element and a printed circuit board, wherein the spiral shaped casing element is mounted to a first surface of the printed circuit board such that a flowpath for the purified air forced by the impeller through the volute is defined by the first surface of the printed circuit board and an interior surface of the spiral shaped casing element; and wherein the motor of the radial fan assembly is located within the volute and the stator is mounted on the first surface of the printed circuit board; wherein the radial fan assembly is axially located in a space enclosed between the front casing and the back casing and the filter assembly is mounted on a front face of the front casing, such that the filter assembly resides outside the space enclosed between the back casing and the front casing in which the radial fan assembly resides. 